This invention relates to a unique steering knuckle for a heavy vehicle steering system wherein the relative position of the kingpin boss and the other steering components is adjustable.
Heavy vehicle steering systems typically include a pair of wheel end assemblies on the steering axle. The wheel end assemblies are mounted on the knuckle, which includes two bosses mounted onto a kingpin. A lower boss is spaced from an upper boss. The standard structure available today includes a one-piece steering knuckle combined with the upper and lower bosses. There is no adjustability. An I-beam extends across the vehicle, and is positioned between the upper and lower boss, and also about the kingpin at each end. The two lower bosses are connected to a tie rod, and the two upper bosses are connected to a steering arm. Current steering systems utilize the kingpin bosses to allow rotation of the knuckle and wheel end assembly about the kingpin, thus resulting in steering of the vehicle.
There are a number of dimensional differences between the steering systems on different vehicles. As one example, the I-beam has a drop dimension along its length. There are a number of different drops requested by heavy vehicle manufacturers for the I-beam. The drop could be characterized as the distance between the spring pad of the I-beam and the rotational axis of the wheel on the wheel hub. The requests for different drops have resulted in a need for a large number of different I-beam forgings. Further, as the I-beam drop is increased, a cross tube, which is a portion of the steering assembly connected into the tie rod assembly, may also be in interference with the spring pad, oil pan and/or other vehicle components.
As another example, the steering arm which is connected to the upper kingpin boss is also desirably spaced at a variety of different dimensional spacings relative to the spring pad in different vehicles. That is, vehicles manufacturers would like to have freedom in selecting different distances between the steering arm and the spring pad. However, the present structures have not provided any such variation. Instead, numerous steering arms have been constructed to provide the variation.
In a disclosed embodiment of this invention, at least the lower boss of a kingpin boss assembly is adjustable in its positioning relative to the rotational axis for the wheel hub. As the lower boss position is varied, the location of the I-beam and thus the resultant drop can also be varied. In this way, a number of different I-beam drops can be achieved with a single I-beam. The elimination of the requirement of making several different I-beams greatly reduces the expense and burden of manufacturing steering systems for heavy vehicles.
In a preferred embodiment of this invention, the boss may be connected to a flange of the steering knuckle in a variety of different methods after having been positioned at the desired location. In one embodiment, the lower boss may be welded. However, preferably, the lower boss is connected by bolting or other removable mechanisms. In this way, the lower boss can be removed from the knuckle such that a maintenance worker can service the axle components. In one type of front axle, there is a frozen kingpin design where the kingpin is press fit (shrink fit) into the I-beam. In such structure, assembly and maintenance on the combination of the knuckle and the I-beam is complex. The removable lower boss facilitates the assembly and disassembly of the steering assembly.
Preferably, once the vehicle design has been complete, the approximate location of the lower boss portion to achieve a desired drop is determined. In preferred embodiments, a bolt hole on the lower boss is positioned relative to the lower flange of the knuckle. At that time, a hole is drilled through the flange such that the lower boss will be properly positioned to the flange. This is then done as part of the final machining on the knuckle for the entire run of steering assemblies for that vehicle type. As the position of the lower boss moves relative to the flange, spacers may be positioned between the I-beam and the upper boss. Thus, different I-beam configurations are not necessary to achieve different drops.
In other embodiments, a plurality of bolt holes may be formed within the flange such that any one of several different locations can be selected, without having to machine the knuckles to be different for different vehicles. Further, the flanges could be formed with bolt hole slots which allow adjustment of the boss along the slots. Also, the lower boss can be simply welded at the desired location. However, most preferably, the single bolt hole which is machined for a desired position for the particular vehicle combination is preferred.
In another feature of this invention, the upper boss may also be removably mounted to the knuckle. In such an application, the boss may be mounted in any of the fashions described above. By adjustably mounting the upper boss, one can control the distance between the steering arm and the spring pad. There is a desire to have the ability to vary this distance, and to date, this desire has been accommodated by providing different steering arm constructions. By allowing adjustment of the upper boss, the need for a number of different steering arm configurations will be reduced.
These and other features of the present invention can be best understood from the following specification and drawings.